Encode and Decode base 64 in Node JS - arrays

Question

I have a node JS program to concat a String to an encrypted message and base-64 encoding it. in my server program when I tried to base-64 decode, i am not getting the originally generated encrypted message.
i have replicated that problem in simple program below.
In this program,
I pass an encrypted and base 64 encoded message,
decode them, concatenating another string
encode the finalMessage
decode the finalMessage
Split them to get the encrypted message
encode the encrypted message to compare with original message.
the Result is - the original message passed to this function is not the same as the final message.
function decodeAndEncode(message) {
console.log("message---"+message)
const buffer = Buffer.from(message, 'base64');
console.log("buffer---"+buffer)
const updatedStringBuffer = Buffer.from('648f3ec157637553f170bccfe56bc32058d11741d016bf120e7001148b19a4d1');
const finalEncodedMsg = Buffer.from(updatedStringBuffer+"|"+buffer).toString('base64')
console.log("updatedMessage ---"+finalEncodedMsg);
const updatedMessageBuffer = Buffer.from(finalEncodedMsg, 'base64');
console.log("updatedMessageBuffer ---"+updatedMessageBuffer);
const getBackOriginalMsg = updatedMessageBuffer.toString('utf-8',updatedStringBuffer.length+1);
console.log("getBackOriginalMsg---"+getBackOriginalMsg);
const encodedMessageBack = Buffer.from(getBackOriginalMsg).toString('base64')
console.log("encodedMessageBack--- "+encodedMessageBack)
}
const message = 'KCof0N56Z0X5piDvPO4FRL6e80oOxxPzzTMie+QRUy00RzwBn1qubNTtt8z5J+LykqlbcWSWfjGarNr4c40I+RdrI+Fi1r/wCs2ql0kvYYapTaaz9lT2EeMuwTp//kyVDUxaaHmBGaN1Ai7DQz44yKAwAnStWFP/lAuxLReQFp4A8wg9e22irkvC3bIMgpKUIheo/58WD03roH5IQsfIsY7oveODIR5s+T1lmIYBBH0IXZqwDOQpArcy82RMMCme6unhJZPIsWqSlVAEWtD89muXdnpvQRFH88exZ1v3WiYYnlJruFoGz7Yi19nrvYI9gkhoee5Idi2m1w1LmDw8EQ==';
const enc = decodeAndEncode(message)